A Practical Method for Building the FE-Based Phase Variable Model of Single Phase Transformers for Dynamic Simulations

A finite-element (FE)-based phase variable model of single-phase transformers is developed for fast and accurate dynamic simulation purposes. In the developed model, the winding flux linkages, psi₁ and psi₂ are used as the phase variables. Their values are obtained from a series of nonlinear FE computation over the full operating range of the transformer. An equivalent magnetizing current, i_em is defined. The variation of flux linkages psi ₁ and psi₂ with the defined i_em and the primary current i₁ or the secondary current i₂ are used to describe the magnetization nonlinearity of the core. Our study shows that the utilization of iem enables the FE-based phase variable model has the same accuracy as the full FE model without the necessity of excessive number of FE computations. The validity of the developed FE-based circuit model is verified through comparing with the full FE model and demonstrated by simulating the inrush current and the magnetizing currents at various saturation levels